Date: Wed, 12 Jul 2017 20:44:06 +0800
From: Boqun Feng <boqun.feng@gmail.com>
To: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Olof Johansson <olof@lixom.net>, Arnd Bergmann <arnd@arndb.de>,
        akpm@linux-foundation.org, albert@sifive.com,
        yamada.masahiro@socionext.com, mmarek@suse.com, will.deacon@arm.com,
        peterz@infradead.org, mingo@redhat.com, daniel.lezcano@linaro.org,
        tglx@linutronix.de, jason@lakedaemon.net, marc.zyngier@arm.com,
        gregkh@linuxfoundation.org, jslaby@suse.com, davem@davemloft.net,
        mchehab@kernel.org, sfr@canb.auug.org.au, fweisbec@gmail.com,
        viro@zeniv.linux.org.uk, mcgrof@kernel.org, dledford@redhat.com,
        bart.vanassche@sandisk.com, sstabellini@kernel.org,
        daniel.vetter@ffwll.ch, mpe@ellerman.id.au, msalter@redhat.com,
        nicolas.dichtel@6wind.com, james.hogan@imgtec.com,
        paul.gortmaker@windriver.com, linux@roeck-us.net,
        heiko.carstens@de.ibm.com, schwidefsky@de.ibm.com,
        linux-kernel@vger.kernel.org, patches@groups.riscv.org
Subject: Re: [PATCH 10/17] RISC-V: Atomic and Locking Code
Message-ID: <20170712124406.jectd7nj4wfx5ign@tardis>
References: <20170712013130.14792-1-palmer@dabbelt.com>
 <20170712013130.14792-11-palmer@dabbelt.com>
 <20170712124049.i7taml22aat2bcgt@tardis>
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On Wed, Jul 12, 2017 at 08:40:49PM +0800, Boqun Feng wrote:
[...]
> > +/**
> > + * set_bit - Atomically set a bit in memory
> > + * @nr: the bit to set
> > + * @addr: the address to start counting from
> > + *
> > + * This function is atomic and may not be reordered.  See __set_bit()
>=20
> This is incorrect, {set,change,clear}_bit() can be reordered, see
> Documentation/memory-barriers.txt, they are just relaxed atomics. But I
> think you just copy this from x86 code, so maybe x86 code needs help
> too, at least claim that's only x86-specific guarantee.
>=20
> > + * if you do not require the atomic guarantees.
> > + *
> > + * Note: there are no guarantees that this function will not be reorde=
red
> > + * on non x86 architectures, so if you are writing portable code,
> > + * make sure not to rely on its reordering guarantees.
> > + *

Hmmm.. the claim is right here ;-/

As your implementation is relax semantics, you'd better rewrite the
comment ;-)

Regards,
Boqun

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